11 Photoresponsive liquid-crystalline block copolymers with hierarchical structures

Block copolymers (BCs) usually self-assemble into nanoscale multistructures upon microphase separation (MPS) in bulk films. However, it is difficult for these nanostructures to be regulated into macroscopic ordering. The introduction of mesogenic ordering combines the responsive feature of liquid crystals under an external stimulus with the MPS characteristics of BCs, providing an elegant method to fabricate highly ordered nanostructures upon hierarchical self-assembly. Because of the excellent capabilities of being adjusted in a noncontact way, photoresponsive liquid-crystalline block copolymers (PLCBCs) especially containing azobenzene chromophores have attracted lots of research interests. The photoresponsive mesogens of azobenzene moieties can help manipulate the ordered MPS nanostructures. Here, we overview the fabrication and photomanipulation of a series of PLCBCs with hierarchical structures. Both polarized and unpolarized light can be utilized to adjust the MPS process. In addition, PLCBCs exhibit various responsiveness under irradiation with a certain wavelength, including photoinduced phase transition, photo-controlled supramolecular cooperative motion, and photo-triggered mass transfer. Based on these light-responsive properties, PLCBCs have been applied in many fields involving photonic materials, information storage, holographic grating, nanotemplates for nanofabrication, and so on.